It is difficult to adhere photographic emulsions to oriented polyester supports, such as polyethylene terephthalate and polyethylene naphthalate. This problem is exacerbated by the conditions to which photographic elements are subjected; i.e., the adhesion must not fail in the raw and processed dry state, as well as when the film is wet during the development process.
Several adhesion promoting "subbing" materials, such as poly(methyl acrylate-co-vinylidene chloride-co-itaconic acid) and poly(acrylonitrile-co-vinylidene chloride-co-acrylic acid) disclosed in U.S. Pat. Nos. 3,201,249 and 3,143,421, respectively, provide the required adhesion when applied before orientation but are not as effective when applied on oriented support. The effectiveness of these adhesive materials may be enhanced by the use of swelling or attack agents such as resorcinol.
An alternative approach disclosed in U.S. Pat. No. 4,695,532 describes a discharged treated polyester film support having coated directly thereon a crosslinked layer of an aqueous vinyl acrylate copolymer and gelatin mixture. Although this system has good adhesion before processing, the adhesion performance is severely degraded by photographic developing solutions.
U.S. Pat. No. 5,639,589 discloses a polyester film support having a surface bearing an improved subbing layer which comprises a mixture of gelatin and a vinyl polymer in which the ratio of gelatin to polymer and the dry coverage of the layer are specified.
EP 0583787 A2 discloses the use of glow discharge treatment to enhance the adhesion of photographic elements. This treatment involves the use of high energy plasma under vacuum which requires specific equipment.
U.S. Pat. No. 5,378,592 discloses the use of a two-layer subbing layer (for photographic materials) wherein the first subbing layer is a layer of polyurethane latex cured with an epoxy compound or a dichloro-s-triazine derivative, and the second subbing layer is a hydrophilic colloid layer comprising gelatin.
U.S. Pat. No. 5,532,118 describes the use of a layer of a self-crosslinking polyurethane as an adhesion promoting material for polyester film support. The polyurethane was not gelatin-grafted nor did the adhesion promoting layer contain gelatin.
It is desirable to provide polyester film supports having improved wet and dry adhesion of hydrophilic colloid emulsions. It is also desirable to provide such supports that are free of photosensitive active materials.
U.S. Pat. Nos. 4,855,219, 5,066,572, 5,248,558, 5,330,885, and others, describe gelatin-coated latex polymers and gelatin-grafted latex polymers and their use in photographic elements. Typically, these latex polymers are either soft or hard (meth)acrylate copolymer latexes that are added to protective overcoats for silver halide emulsion layers to improve resistance to scratch, abrasion, and ferrotyping or are added to interlayers or silver halide emulsion layers to reduce pressure sensitivity.